Well, how cumbersome and how inefficient? There are a number of suggestions made by the other replies, but before I weigh in I would need to know exactly what are your expectations, that is, what do you consider to be "efficient" and "inefficient". You can't just determine this from the APIs, I would need to see some performance metrics.

 For example, you mention ray tracing, however in any scene of even average complexity the computational expense of ray tracing would massively outweigh the bitmap update code.

There are some performance notes on a Reaction Diffusion simulator I wrote on my own website. It uses Joe Stegman's PNGEncoder class, which is sufficient for my needs because the actual simulation code is the bottleneck in this scenario.